US DHS: cyber attacks on Ukraine power firms hit 225,000 customers

The US Department of Homeland Security is warning US firms about cyberattacks on a Ukraine power firms in December that impacted hundreds of thousands of customers, however the BlackEnergy trojan’s role in the attacks remains unclear.

Ever since the December 23 outages at three Ukraine power distribution companies, security experts have suspected it was caused by the BlackEnergy trojan, a notorious and destructive piece of malware used in attacks on industrial control system equipment.

The DHS’ Industrial Control Systems Cyber Emergency Response Team (ICS-CERT) published an alert on Thursday confirming the outages were caused by cyber attackers but it could not determine whether BlackEnergy played a role.

It’s assessment is based on interviews with leaders at six Ukrainian firms affected by the December outage, including the three regional electric power distribution companies directly hit. Local news services at the time reported that a virus disconnected electrical substations.

The interviews were conducted by an interagency team consisting of members from ICS-CERT, the FBI, US-CERT, the Department of Energy, and the North American Electric Reliability Corporation.

“Following these discussions and interviews, the team assesses that the outages experienced on December 23, 2015, were caused by external cyber-attackers,” ICS-CERT said.

“Power outages were caused by remote cyber intrusions at three regional electric power distribution companies (Oblenergos) impacting approximately 225,000 customers,” it added.

Services at the three power distribution firms had been restored however ICS-CERT said the firms were still running under “constrained operations".

ICS-CERT said that all three power distribution companies reported that the KillDisk malware was executed at the conclusion of the attack. This malware wiped select files and corrupt the master boot record of affected systems.

KillDisk has previously been linked to BlackEnergy by Ukraine’s CERT, CERT-UA, which drew a connection in November following attacks on news media companies during Ukraine's 2015 local elections.

ICS-CERT also reported in 2014 that several companies running industrial control systems with a human-machine interface (HMI) from General Electric, Siemens and BroadWin/Advantech had systems infected with BlackEnergy.

In January, Kaspersky Lab researchers reported BlackEnergy was delivered by rigged Microsoft Word documents attached to phishing email. The documents encouraged recipients to enable macros, which would then be used to infect machines.

ICS-CERT said that in at least one instance, Windows-based HMIs embedded in remote terminal units were overwritten with KillDisk.

Other actions also suggested to the US team that the attackers were aiming to stifle recovery following the outage.

“The actors also rendered Serial-to-Ethernet devices at substations inoperable by corrupting their firmware. In addition, the actors reportedly scheduled disconnects for server Uninterruptable Power Supplies (UPS) via the UPS remote management interface. The team assesses that these actions were done in an attempt to interfere with expected restoration efforts,” ICS-CERT said.

All companies interviewed by the US team reported they were infected with BlackEnergy, however ICS-CERT said it could not confirm whether this malware played a role in the attacks.

“It is suspected that BlackEnergy may have been used as an initial access vector to acquire legitimate credentials; however, this information is still being evaluated. It is important to underscore that any remote access Trojan could have been used and none of BlackEnergy’s specific capabilities were reportedly leveraged.” ISC-CERT said.

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